DESCRIPTION: There has been a lot of optimism about potentially eradicating HIV-1 using strategies such as reactivation of latently infected cells by small molecules. A recent study has suggested that this approach may in fact be possible; a single dose of the molecule vorinostat was shown to induce HIV expression in CD4+ T cells in vivo. While this strategy may end up being effective, it may be very challenging to reactivate every last latently infected CD4+ T cell. A complementary strategy may be to physically eliminate latently infected cells using antibodies conjugated to toxins. This may be analogous to surgically debulking a tumor prior to initiating chemotherapy. However, targeting latently infected CD4+ T cells has been a challenging task because the phenotype of these cells remains largely unknown. In this new proposal, we plan to use antibodies to more than 200 different T cell markers in order to determine the phenotype of latently infected CD4+ T cells. Such an approach has been successfully used to determine the phenotype of activated T cells in a recent study. This will be analogous to screening for small molecules that activate latently infected CD4+ T cells, but in this case, a library of monoclonal antibodies (Mabs) rather than compounds will be used and the readout will be binding of Mabs to infected resting CD4+ T cells or recently reactivated latently infected CD4+ T cells rather than reactivation itself. We plan to validate our results by sorting resting CD4+ T cells from HIV-1 infected patients on suppressive HAART regimens. We specifically will sort for markers that are identified in our screen to determine whether there is an overrepresentation of HIV-1 DNA and latent replication-competent virus in these cells. This work will have major implications for strategies for HIV-1 eradication since it will potentially lead to the clearance of latently infectd cells.